CN110927428A - Wide-range wide-band high-precision magnetic balance type current measuring device - Google Patents

Wide-range wide-band high-precision magnetic balance type current measuring device Download PDF

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CN110927428A
CN110927428A CN201911105251.5A CN201911105251A CN110927428A CN 110927428 A CN110927428 A CN 110927428A CN 201911105251 A CN201911105251 A CN 201911105251A CN 110927428 A CN110927428 A CN 110927428A
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magnetic
coil
current
compensation
magnetic ring
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CN110927428B (en
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徐林
王作帅
耿攀
周彤
郑攀峰
肖涵琛
杨文铁
左超
王建勋
余定峰
杨帅
杨勇
孙瑜
魏华
陈涛
罗伟
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719th Research Institute of CSIC
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    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
    • G01R19/00—Arrangements for measuring currents or voltages or for indicating presence or sign thereof
    • G01R19/0092—Arrangements for measuring currents or voltages or for indicating presence or sign thereof measuring current only
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
    • G01R15/00—Details of measuring arrangements of the types provided for in groups G01R17/00 - G01R29/00, G01R33/00 - G01R33/26 or G01R35/00
    • G01R15/14—Adaptations providing voltage or current isolation, e.g. for high-voltage or high-current networks
    • G01R15/18—Adaptations providing voltage or current isolation, e.g. for high-voltage or high-current networks using inductive devices, e.g. transformers
    • G01R15/186—Adaptations providing voltage or current isolation, e.g. for high-voltage or high-current networks using inductive devices, e.g. transformers using current transformers with a core consisting of two or more parts, e.g. clamp-on type
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
    • G01R15/00—Details of measuring arrangements of the types provided for in groups G01R17/00 - G01R29/00, G01R33/00 - G01R33/26 or G01R35/00
    • G01R15/14—Adaptations providing voltage or current isolation, e.g. for high-voltage or high-current networks
    • G01R15/20—Adaptations providing voltage or current isolation, e.g. for high-voltage or high-current networks using galvano-magnetic devices, e.g. Hall-effect devices, i.e. measuring a magnetic field via the interaction between a current and a magnetic field, e.g. magneto resistive or Hall effect devices

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  • Measurement Of Current Or Voltage (AREA)

Abstract

A wide-range broadband high-precision magnetic balance type current measuring device comprises a first magnetic ring (1), a second magnetic ring (2), a third magnetic ring (3), an excitation current source (4), a first excitation coil (5), a first detection coil (6), a first compensation coil (7), a second excitation coil (8), a second detection coil (9), a second compensation coil (10), a third detection coil (11), a third compensation coil (12), a first differential amplifier (13), a first band-pass filter (14), a phase-sensitive wave-picking device (15), a second differential amplifier (16), a second band-pass filter (17), an adder (18), a regulator (19), a driver (20), a compensation current source (21) and a sampling resistor (22). The invention adopts three parallel magnetic rings, detects the magnitude of the current passing through the magnetic rings in a non-contact mode, and can realize large-range, wide-frequency-band, high-precision, high-sensitivity and quick-response measurement of the current to be measured by adopting a compensation method of magnetic balance.

Description

Wide-range wide-band high-precision magnetic balance type current measuring device
Technical Field
The invention relates to the field of signal detection, in particular to a wide-range wide-band high-precision magnetic balance type current measuring device.
Background
The current is one of the most important physical quantities in the electrical field, and the working states of equipment, loads, lines and the like can be intuitively reflected through the current in each link of power generation, power transmission, power transformation, power distribution, power utilization and the like. How to accurately and rapidly detect steady-state direct current, low-frequency alternating current, high-frequency alternating current, leakage current, instantaneous current, pulse current and the like has become one of the most important research hotspots in the power industry.
Generally, methods for measuring current signals are mainly classified into two types: contact measurement and non-contact measurement. The typical contact measurement method mainly comprises the following steps: resistance method, shunt method, current transformer method. The resistance method is characterized in that a precise resistor is connected in series in a current loop to be measured, and the magnitude of the current to be measured can be obtained by measuring the voltage at two ends of the resistor; the shunt method is similar to the resistance method, only adopts high-temperature-resistant and high-conductivity materials to manufacture, can solve the heating problem in the resistance method, but has low sensitivity and large error in low-current test because the resistance value is generally low; the current transformer method is based on Faraday's law of electromagnetic induction, and is characterized in that a transformer is connected in series in a measured current loop, so that the change of the measured current causes the change of magnetic flux in the transformer, a voltage signal is induced in a secondary loop of the transformer, the magnitude of the measured current can be inverted by measuring the magnitude of the voltage, and the current transformer method can realize the measurement of wide-range alternating current, but has low measurement precision, poor linearity and lower resolution.
In the scheme of measuring the current in a non-contact manner, the magnitude of the current is usually inverted by measuring the magnetic field generated by the measured current, and the magnetic field generated by the measured current is usually measured by using a fluxgate or a magnetoresistive sensor. However, the magnetic field generated in the surrounding space by the measured current is measured by the magnetic sensor, which can seriously affect the measurement accuracy and resolution and is easily interfered by the environment. The magnetic gathering ring is adopted to gather the magnetic field generated by the measured current in the space, and then the magnetic field is measured in the air gap of the magnetic gathering ring, so that the magnitude of the measured current can be calculated. The method can effectively improve the sensitivity of the system, but the volume of the measuring device is generally larger, and the method is not suitable for occasions with strict requirements on space dimensions, such as the internal current of equipment, leakage current, cable current and the like. Another method for inverting the measured current by measuring the magnetic field is based on the magnetic modulation principle, and the method is characterized in that high-frequency large-amplitude alternating excitation current is conducted to a closed high-permeability magnetic core, so that the magnetic core is in periodic symmetric saturation, the magnetic field generated by the measured current is superposed on the excitation magnetic field, periodic asymmetric saturation occurs to the magnetic core, the periodic asymmetric saturation magnetic flux is analyzed, the maximum amplitude of a secondary component (the frequency of the excitation current is used as the fundamental frequency) can be found, and the amplitude of the secondary component can be extracted to invert the magnitude of the measured current. The measurement method can also realize high precision and high resolution by reasonable design, and the volume can be obviously reduced, but the method also has the problems of low bandwidth, low frequency response and the like.
In the non-contact measurement scheme, a common problem exists, namely the contradiction between large range and high sensitivity. To achieve high sensitivity, the measurement circuit is inevitably required to have a large amplification factor, but the high amplification factor makes the measurement device easily saturate when detecting a large current, which restricts the range of the measurement device. In addition, in the non-contact measurement scheme, by using a method for measuring a magnetic field inversion current, the bandwidth of the measurement device is limited by the sensor itself or the magnetic modulation characteristics no matter whether the magnetic field is directly measured by using a magnetic sensor or based on the magnetic modulation principle, and it is difficult to measure direct current, low-frequency alternating current and high-frequency alternating current at the same time.
In summary, for the current measurement occasions with wide range and wide frequency band, and simultaneously considering the requirements of wide range, high precision and high sensitivity, the conventional measurement method is difficult to meet the requirements, and a new measurement method needs to be provided.
Disclosure of Invention
The invention aims to provide a wide-range, wide-frequency and high-precision current measuring device aiming at non-contact, wide-range and alternating current and direct current measuring occasions.
Specifically, the invention provides a wide-range broadband high-precision magnetic balance type current measuring device which comprises a first magnetic ring (1), a second magnetic ring (2), a third magnetic ring (3), an excitation current source (4), a first excitation coil (5), a first detection coil (6), a first compensation coil (7), a second excitation coil (8), a second detection coil (9), a second compensation coil (10), a third detection coil (11), a third compensation coil (12), a first differential amplifier (13), a first band-pass filter (14), a phase-sensitive wave detector (15), a second differential amplifier (16), a second band-pass filter (17), an adder (18), a regulator (19), a driver (20), a compensation current source (21) and a sampling resistor (22),
the first magnetic ring (1), the second magnetic ring (2) and the third magnetic ring (3) are pasted together in parallel, and the current I to be measuredpPasses through the three magnetic rings to generate magnetic fields H with the same size in the three magnetic ringsp；
The first excitation coil (5), the first detection coil (6) and the first compensation coil (7) are wound on the surface of the first magnetic ring (1);
the second excitation coil (8), the second detection coil (9) and the second compensation coil (10) are wound on the surface of the second magnetic ring (2);
the second detection coil (11) and the third compensation coil (12) are wound on the surface of the third magnetic ring (3);
one end of the first exciting coil (5) is connected with the output anode of the exciting current source (4), the other end of the first exciting coil is connected with one end of the second exciting coil (8), and the other end of the second exciting coil (8) is connected with the output cathode of the exciting current source (4);
one end of the first detection coil (6) is connected with the positive input end of the first differential amplifier (13), the other end of the first detection coil is connected with one end of the second detection coil (9), and the other end of the second detection coil (9) is connected with the negative input end of the first differential amplifier (13);
the first compensation coil (7), the second compensation coil (10) and the third compensation coil (12) are respectively connected in series, namely the tail end of the third compensation coil (12) is connected with the head end of the second compensation coil (10), the tail end of the second compensation coil (10) is connected with the head end of the first compensation coil (7), the tail end of the first compensation coil (7) is connected with the positive end of the sampling resistor (22), and the negative end of the sampling resistor (22) is connected with the output negative electrode of the compensation current source (21); the head end of the third compensation coil (12) is connected with the output positive electrode of the compensation current source (21);
the output end of the first differential amplifier (13) is connected with the input end of the first band-pass filter (14); the output end of the first band-pass filter (14) is connected with the input end of the phase sensitive detector (15);
two ends of the third detection coil (11) are respectively connected with the input end of the second differential amplifier (16), and the output end of the second differential amplifier (16) is connected with the second band-pass filter (17);
the output end of the phase-sensitive detector (15) and the output end of the second band-pass filter (17) are respectively connected to the adder (18);
the output end of the adder (18) is connected with the input end of the regulator (19); the output end of the regulator (19) is connected with the input end of the driver (20); the output end of the driver (20) is connected to the input end of the compensation current source (21).
Furthermore, the first magnetic ring (1), the second magnetic ring (2) and the third magnetic ring (3) are three identical magnetic rings;
the number of turns of the first excitation coil (5) is completely the same as that of the second excitation coil (8), and the number of turns of the first detection coil (6) is completely the same as that of the second detection coil (9); the number of turns of the first compensation coil (7) is identical to that of the second compensation coil (10);
the excitation current source (4) is used for generating high-frequency periodically alternating excitation current Ie in the first excitation coil (5) and the second excitation coil (8), the current generates a high-frequency periodically alternating excitation magnetic field He in the first magnetic ring (1) and the second magnetic ring (2), and the amplitude of the excitation magnetic field is far larger than the saturation magnetic field value of the first magnetic ring (1) and the second magnetic ring (2), so that the first magnetic ring (1) and the second magnetic ring (2) are periodically saturated;
the first magnetic ring (1), the second magnetic ring (2), the first compensating coil (7) and the second compensating coil (10) are used for measuring direct current; the third magnetic ring (3) and the third compensation coil (12) are used for measuring alternating current.
Furthermore, after the external power supply, the excitation current source (4) generates periodic excitation current I to the first excitation coil (5) and the second excitation coil (6)e＝Imsin ω t, where ω ═ 2 π fe，feTo frequency of the excitation current, ImThe excitation current respectively generates excitation magnetic fields H with equal magnitude and opposite directions in the first magnetic ring (1) and the second magnetic ring (2) for amplitudee＝Hmsinωt，HmIs the amplitude of the excitation magnetic field;
at the measured current IpWhen equal to 0, the magnetic field H generated by the side current p0; the magnetic induction intensity B in the first magnetic ring (1) and the second magnetic ring (2)1And B2Respectively as follows:
B1＝B2＝μHmsin ω t type (1)
Mu in the formula (1) is the magnetic conductivity of the three magnetic rings;
the magnetic induction intensity B1Induced electromotive force U generated in the first detection coil (6)O1Comprises the following steps:
Figure BDA0002269331730000051
n in the formula (2)12The number of turns of the first detection coil (6) and the second detection coil (9) is set, and S is the sectional area of the three magnetic rings;
the magnetic induction intensity B2Induced electromotive force U generated in the second detection coil 9O2Comprises the following steps:
Figure BDA0002269331730000061
the input signal U of said first differential amplifier (13)in1Comprises the following steps:
Uin1＝UO1+UO2formula (4)
From the expressions (2) to (4), it can be seen that the current signal I is applied to the target sidepIn the case of 0, the input signal U of the first differential amplifier (13)in1＝0；
At the measured current IpWhen equal to 0, the magnetic field H generated by the side currentpWhen the magnetic induction is 0, the magnetic induction intensity B in the third magnetic ring (3)3When the value is 0, the induced electromotive force U at the two ends of the third detection coil (11) isO3Comprises the following steps:
Figure BDA0002269331730000062
n in formula (5)3The number of turns of the third detection coil (11);
the input signal U of said second differential amplifier (16)in2＝UO3＝0；
The output signal of the first differential amplifier (13) passes through the first band-pass filter (14) and the phase sensitive detector (15), and then the output signal U is outputx1＝0；
The output signal of the second differential amplifier (16) passes through the second band-pass filter (17), and then the output signal U is outputx2＝0；
The output signal Ux1And Ux2After passing through the adder (18), the regulator (19) and the driver (20), the compensation current I output by the compensation current source (21) is still zerocWhen the voltage U is equal to 0, the voltage U is between the two ends of the sampling resistor (22)OS0; i.e. when said measured current IpWhen the value is 0, the output of the current measuring device according to the present invention is also 0.
Further, when the measured current IpWhen the magnetic field is not equal to 0 and is a direct current signal, the magnetic fields generated in the first magnetic ring (1), the second magnetic ring (2) and the third magnetic ring (3) are all Hp；
In the excitation magnetic field HeAnd said magnetic field HpUnder the combined action of the first magnet and the second magnetMagnetic induction B in the ring (1)1Comprises the following steps:
B1＝μ(Hp+Hmsin ω t) type (6)
The magnetic induction intensity B in the second magnetic ring (2)2Comprises the following steps:
B2＝μ(Hp-Hmsin ω t) type (7)
The magnetic induction intensity B1Induced electromotive force U generated by acting on the first detection coil (6)O1Comprises the following steps:
Figure BDA0002269331730000071
the magnetic induction intensity B2Induced electromotive force U generated in the second detection coil (9)O2Comprises the following steps:
Figure BDA0002269331730000072
the amplitude H of the excitation magnetic fieldmIs far larger than the saturated magnetic field intensity H of the first magnetic ring (1) and the second magnetic ring (2)s(ii) a At the moment, the first magnetic ring (1) and the second magnetic ring (2) are in a non-saturated state and a saturated state to periodically alternate, and the magnetic permeability mu of the first magnetic ring and the second magnetic ring also periodically changes between a linear region and a non-linear region, wherein the magnetic permeability mu can be expressed as:
Figure BDA0002269331730000073
in the formula (10) < mu >dcIs the direct current component of the magnetic permeability, μiIs the 2 i-th harmonic component of the permeability; by substituting formula (10) for formula (8) and formula (9), respectively:
Figure BDA0002269331730000074
Figure BDA0002269331730000081
said first differential amplifier (13) inputting a signal Uin1Comprises the following steps:
Figure BDA0002269331730000082
the input signal Uin1After passing through the first differential amplifier (13), proportional amplification is carried out, and then, after passing through the first band-pass filter (14), harmonic components for 4 times or more are filtered out, and only 2-time components are reserved; the phase sensitive detector (15) extracts the amplitude of the 2-time component and outputs a signal Ux1Comprises the following steps:
Ux1＝K1Uin1＝4K1N12SHpωμ1formula (14)
Formula (14) K1Is the amplification factor of the first differential amplifier (13), mu1Is a secondary component of the permeability;
when the measured current IpWhen the signal is a direct current signal, the magnetic induction intensity B generated in the third magnetic ring (3) is3The induced electromotive force U is generated after passing through the third detection coil (11) and is kept unchangedO30; then the signal U is output after passing through the second differential amplifier (16) and the second band-pass filter (17)x2＝0。
Furthermore, when the measured current IpWhen the magnetic field generated by the magnetic field generator is not equal to 0 and is an alternating current signal, the magnetic field generated by the magnetic field generator in the third magnetic ring is HpThe magnetic induction intensity B of the magnetic field generated in the third magnetic ring (3)3＝μHp(ii) a The magnetic induction intensity B3The induced electromotive force generated at the two ends of the third detection coil (11) is as follows:
Figure BDA0002269331730000083
the U isO3The signal is amplified in proportion after passing through the second differential amplifier (16), and then passes through the second differential amplifierAfter the second band-pass filter (17), filtering out UO3Obtaining a signal U by low-frequency components and high-frequency noise components in the signalx2Comprises the following steps:
Figure BDA0002269331730000091
k in formula (16)3Is the amplification of said second differential amplifier (16).
Furthermore, when the measured current IpIn the case of a DC signal, U is expressed by equations (6) to (13)x1＝4K1N12SHpωμ1，U x20; the signal Ux1And Ux2After being superposed by the adder (18), the signals are amplified by the regulator (19), and then are generated into driving signals by the driver (20) to drive the compensation current source (21) to generate compensation current Ic(ii) a The compensation current IcGenerating a compensating magnetic field Hc(ii) a The compensation magnetic field HcMagnetic field H generated by current to be measuredpIn the opposite direction, equation (14) can be rewritten as:
Ux1＝K1Uin1＝4K1N12S(Hp-Hc)ωμ1formula (17)
Provided that U in the formula (14)x1If the signal is not zero, the signal passes through the adder (18), the regulator (19) and the driver (20) and then drives the compensation current source (21) to generate the compensation current IcAnd then produce and HpCompensating magnetic field H with opposite directionsResult in Ux1Reducing to finally reach dynamic magnetic field balance, so that U is formedx1Approaching 0, i.e. Hp＝Hs(ii) a Said Hp、HsWith said measured current Ic、IpThe relationship of (1) is: hp＝Kp×Ip，Hc＝Kc×Ic，Kp、KcThe linear coefficient can be calibrated according to the original measurement data;
the sampling circuitA voltage U across the resistor (22)OS＝Ic×Rs，RsThe resistance value of the sampling resistor (22) is further calculated to know the measured current IpComprises the following steps:
Figure BDA0002269331730000092
from the equation (18), by measuring the sampling resistance RsVoltage U acrossosThe measured current I can be invertedpThe size of (2).
Furthermore, when the measured current IpWhen the signal is an alternating current signal, the signal Ux2As shown in equation (16), the signal passes through the adder (18), the regulator (19) and the driver (20) to generate a driving signal, and then drives the compensation current source (21) to generate a compensation current Ic(ii) a The compensation current IcGenerating a compensation magnetic field H in said third detection coil (11)c(ii) a The compensation magnetic field and the measured current IpThe generated magnetic field HpIn the opposite direction, equation (16) can be rewritten as:
Figure BDA0002269331730000101
under the action of the regulator (19), the driver (20) and the compensation current source (20), the third magnetic ring (3) finally achieves dynamic magnetic balance, namely Hp is Hc; according to the ampere-loop theorem, N can be known3×Ic＝IpIn the formula Ns3The number of turns of the third compensation coil (12); the voltage U at two ends of the sampling resistor (22)OSComprises the following steps: u shapeOS＝Ic×RsFurther calculating the measured current IpComprises the following steps:
Figure BDA0002269331730000102
from the equation (20), by measuring the sampling resistance RsVoltage acrossUOSThe measured current I can be invertedpThe size of (2).
The invention has the advantages that:
1) non-contact measurement of the measured current is realized;
2) the device can measure direct current, alternating current and pulse current;
3) a high-permeability magnetic ring is adopted, a magnetic circuit is completely closed, and high-precision measurement is realized based on the magnetic balance principle;
4) for the detection of direct current, two magnetic rings are adopted, an excitation coil connected in series in the reverse direction and a detection coil connected in series in the forward direction are designed, the influence of a transformer effect is counteracted, and the effective sensitivity of measurement is doubled;
5) for alternating current, a magnetic ring is designed independently, and based on the magnetic balance principle, the measurement of high-frequency alternating current can be realized, and the frequency band and the response speed of the measuring device are high;
6) the measurement of large current is realized by adopting the magnetic balance principle; due to the adoption of the magnetic ring with high magnetic conductivity, the ultrahigh sensitivity can be realized by matching with the design of a differential amplifier, a regulator, a compensating current source and the like; the measuring device solves the problem that the conventional measuring equipment cannot achieve both wide range and high sensitivity.
Drawings
FIG. 1 shows a wide-band high-precision magnetic balance type current measuring device
FIG. 2 is a graph showing the variation of magnetic permeability of a magnetic ring with magnetic field intensity
FIG. 3 is a graph showing induced electromotive force curves at two ends of the first detection coil and the second detection coil when the detected current is zero
FIG. 4 is a graph showing induced electromotive force curves at two ends of the first detecting coil when the measured current is not zero
FIG. 5 is a graph showing the induced electromotive force curves at two ends of the second detection coil when the measured current is not zero
Detailed Description
The technical solution of the present invention will be described in more detail with reference to the accompanying drawings.
FIG. 1 shows a broadband high-precision magnetic balance type current measuring device according to the present invention, which comprises a first magnetic ring (1), a second magnetic ring (2), a third magnetic ring (3), an excitation current source (4), a first excitation coil (5), a first detection coil (6), a first compensation coil (7), a second excitation coil (8), a second detection coil (9), a second compensation coil (10), a third detection coil (11), a third compensation coil (12), a first differential amplifier (13), a first band-pass filter (14), a phase sensitive filter (15), a second differential amplifier (16), a second band-pass filter (17), an adder (18), a regulator (19), a driver (20), a compensation current source (21), and a sampling resistor (22),
the first magnetic ring (1), the second magnetic ring (2) and the third magnetic ring (3) are pasted together in parallel, and the current I to be measuredpPasses through the three magnetic rings to generate magnetic fields H with the same size in the three magnetic ringsp；
The first excitation coil (5), the first detection coil (6) and the first compensation coil (7) are wound on the surface of the first magnetic ring (1);
the second excitation coil (8), the second detection coil (9) and the second compensation coil (10) are wound on the surface of the second magnetic ring (2);
the second detection coil (11) and the third compensation coil (12) are wound on the surface of the third magnetic ring (3);
one end of the first exciting coil (5) is connected with the output anode of the exciting current source (4), the other end of the first exciting coil is connected with one end of the second exciting coil (8), and the other end of the second exciting coil (8) is connected with the output cathode of the exciting current source (4);
one end of the first detection coil (6) is connected with the positive input end of the first differential amplifier (13), the other end of the first detection coil is connected with one end of the second detection coil (9), and the other end of the second detection coil (9) is connected with the negative input end of the first differential amplifier (13);
the first compensation coil (7), the second compensation coil (10) and the third compensation coil (12) are respectively connected in series, namely the tail end of the third compensation coil (12) is connected with the head end of the second compensation coil (10), the tail end of the second compensation coil (10) is connected with the head end of the first compensation coil (7), the tail end of the first compensation coil (7) is connected with the positive end of the sampling resistor (22), and the negative end of the sampling resistor (22) is connected with the output negative electrode of the compensation current source (21); the head end of the third compensation coil (12) is connected with the output positive electrode of the compensation current source (21);
the output end of the first differential amplifier (13) is connected with the input end of the first band-pass filter (14); the output end of the first band-pass filter (14) is connected with the input end of the phase sensitive detector (15);
two ends of the third detection coil (11) are respectively connected with the input end of the second differential amplifier (16), and the output end of the second differential amplifier (16) is connected with the second band-pass filter (17);
the output end of the phase-sensitive detector (15) and the output end of the second band-pass filter (17) are respectively connected to the adder (18);
the output end of the adder (18) is connected with the input end of the regulator (19); the output end of the regulator (19) is connected with the input end of the driver (20); the output end of the driver (20) is connected to the input end of the compensation current source (21);
the first magnetic ring (1), the second magnetic ring (2) and the third magnetic ring (3) are three identical magnetic rings, and can be made of nanocrystalline or permalloy materials with high magnetic conductivity and low coercive force;
the number of turns of the first excitation coil (5) is completely the same as that of the second excitation coil (8), and the number of turns of the first detection coil (6) is completely the same as that of the second detection coil (9); the number of turns of the first compensation coil (7) is identical to that of the second compensation coil (10); the exciting coil, the detecting coil and the compensating coil can be wound by enameled wires with high conductivity;
the excitation current source (4) is configured to generate a high-frequency periodically alternating excitation current Ie in the first excitation coil (5) and the second excitation coil (8), the current generates a high-frequency periodically alternating excitation magnetic field He in the first magnetic ring (1) and the second magnetic ring (2), and the amplitude of the excitation magnetic field is much larger than the saturation magnetic field value of the first magnetic ring (1) and the second magnetic ring (2), so that the first magnetic ring (1) and the second magnetic ring (2) periodically alternate between a saturated state and an unsaturated state, as shown in fig. 3;
the first magnetic ring (1), the second magnetic ring (2), the first compensating coil (7) and the second compensating coil (10) are used for measuring direct current; the third magnetic ring (3) and the third compensation coil (12) are used for measuring alternating current.
After being supplied with power from the outside, the excitation current source (4) generates periodic excitation current I to the first excitation coil (5) and the second excitation coil (6)e＝Imsin ω t, where ω ═ 2 π fe，feTo frequency of the excitation current, ImThe excitation current respectively generates equal and opposite excitation magnetic fields He-H in the first magnetic ring (1) and the second magnetic ring (2) for amplitudemsinωt，HmIs the amplitude of the excitation magnetic field;
at the measured current IpWhen equal to 0, the magnetic field H generated by the side currentp0; the magnetic induction intensity B in the first magnetic ring (1) and the second magnetic ring (2)1And B2Respectively as follows:
B1＝B2＝μHmsin ω t type (1)
Mu in the formula (1) is the magnetic conductivity of the three magnetic rings;
the magnetic induction intensity B1Induced electromotive force U generated in the first detection coil (6)O1Comprises the following steps:
Figure BDA0002269331730000141
n in the formula (2)12The number of turns of the first detection coil (6) and the second detection coil (9) is set, and S is the sectional area of the three magnetic rings;
the magnetic induction intensity B2Induced electromotive force U generated in the second detection coil 9O2Comprises the following steps:
Figure BDA0002269331730000142
the input signal U of said first differential amplifier (13)in1Comprises the following steps:
Uin1＝UO1+UO2formula (4)
From the expressions (2) to (4), it can be seen that the current signal I is applied to the target sidepIn the case of 0, the input signal U of the first differential amplifier (13)in10; it can also be seen from the graph shown in fig. 3: when the measured current signal is zero, the phases of the induced electromotive force at the two ends of the first detection coil (6) and the second detection coil (9) are just opposite, and the two signals are just offset after being superposed;
at the measured current IpWhen equal to 0, the magnetic field H generated by the side currentpWhen the magnetic induction is 0, the magnetic induction intensity B in the third magnetic ring (3)3When the value is 0, the induced electromotive force U at the two ends of the third detection coil (11) isO3Comprises the following steps:
Figure BDA0002269331730000151
n in formula (5)3The number of turns of the third detection coil (11);
the input signal U of said second differential amplifier (16)in2＝UO3＝0；
The output signal of the first differential amplifier (13) passes through the first band-pass filter (14) and the phase sensitive detector (15), and then the output signal U is outputx1＝0；
The output signal of the second differential amplifier (16) passes through the second band-pass filter (17), and then the output signal U is outputx2＝0；
The output signal Ux1And Ux2Through the saidWhen the adder (18), the regulator (19) and the driver (20) are still zero, the compensation current Ic output by the compensation current source (21) is equal to 0, and the voltage U at the two ends of the sampling resistor (22) is at the moment OS0; i.e. when said measured current IpWhen the output of the current measuring device is 0, the output of the current measuring device is also 0;
through the analysis, when the measured current is zero, the voltage signal output by the measuring device is also zero.
When the measured current IpWhen the magnetic field is not equal to 0 and is a direct current signal, the magnetic fields generated in the first magnetic ring (1), the second magnetic ring (2) and the third magnetic ring (3) are all Hp；
In the excitation magnetic field HeAnd said magnetic field HpUnder the combined action of the magnetic flux and the magnetic induction intensity B in the first magnetic ring (1)1Comprises the following steps:
B1＝μ(Hp+Hmsin ω t) type (6)
The magnetic induction intensity B in the second magnetic ring (2)2Comprises the following steps:
B2＝μ(Hp-Hmsin ω t) type (7)
The magnetic induction intensity B1Induced electromotive force U generated by acting on the first detection coil (6)O1Comprises the following steps:
Figure BDA0002269331730000152
the magnetic induction intensity B2Induced electromotive force U generated in the second detection coil (9)O2Comprises the following steps:
Figure BDA0002269331730000161
the amplitude H of the excitation magnetic fieldmIs far larger than the saturated magnetic field intensity H of the first magnetic ring (1) and the second magnetic ring (2)s(ii) a At the moment, the first magnetic ring (1) and the second magnetic ring (2) are in a period between an unsaturated state and a saturated stateA linear alternation whose permeability μ will also vary periodically between a linear region and a non-linear region, as shown in fig. 2; as can be seen from fig. 2, the permeability curve is symmetrical along the vertical axis, and fourier transform is performed on the permeability curve, so that the permeability curve is found to have a direct current component and an even harmonic component, and the permeability μ can be expressed as:
Figure BDA0002269331730000162
in the formula (10) < mu >dcIs the direct current component of the magnetic permeability, μiIs the 2 i-th harmonic component of the permeability; by substituting formula (10) for formula (8) and formula (9), respectively:
Figure BDA0002269331730000163
Figure BDA0002269331730000164
as can be seen from FIGS. 4 and 5, the magnetic field Hp generated by the measured current and the excitation magnetic field HeUnder the combined action of the first magnetic ring (1) and the second magnetic ring (2), the saturation time and the saturation duration of the positive half-wave and the negative half-wave of the first magnetic ring (1) and the second magnetic ring (2) are changed, so that the induced electromotive force U is generatedO1And UO2The waveform of (2) is shifted, and Fourier transform analysis is performed on the waveform to find UO1Except for even harmonic component, the signal has odd harmonic component and the signal which is generated by 'transformer effect' and has the same frequency with the excitation frequency, and the existence of the signal can influence the final measurement result;
said first differential amplifier (13) inputting a signal Uin1Comprises the following steps:
Figure BDA0002269331730000171
the formula (13) shows that by adopting two sets of exciting coils and two sets of detecting coils, the effective sensitivity of the measuring device is doubled, and the influence of the transformer effect is eliminated;
the first band-pass filter (14) is designed to be [2f ] for the frequency of the signal passing throughe-fb，2fe+fb]Wherein f isbFor the bandwidth value, i.e. the band-pass filter (14) only retains the frequency of the excitation frequency f for the passing signaleFor other signals, after passing through the band-pass filter (15), the signal attenuation is zero;
the input signal Uin1After passing through the first differential amplifier (13), proportional amplification is carried out, and then, after passing through the first band-pass filter (14), harmonic components for 4 times or more are filtered out, and only 2-time components are reserved;
the phase sensitive detector (15) extracts the amplitude of the 2-time component and outputs a signal Ux1Comprises the following steps:
Ux1＝K1Uin1＝4K1N12SHpωμ1formula (14)
Formula (14) K1Is the amplification factor of the first differential amplifier (13), mu1Is a secondary component of the permeability;
when the measured current IpWhen the signal is a direct current signal, the magnetic induction intensity B generated in the third magnetic ring (3) is3The induced electromotive force U is generated after passing through the third detection coil (11) and is kept unchangedO30; then the signal U is output after passing through the second differential amplifier (16) and the second band-pass filter (7)x2＝0。
Furthermore, when the measured current IpWhen the magnetic field generated by the magnetic field generator is not equal to 0 and is an alternating current signal, the magnetic field generated by the magnetic field generator in the third magnetic ring is HpThe magnetic induction intensity B of the magnetic field generated in the third magnetic ring (3)3＝μHp(ii) a The magnetic induction intensity B3The induced electromotive force generated at the two ends of the third detection coil (11) is as follows:
Figure BDA0002269331730000181
the U isO3The signal is amplified in proportion after passing through the second differential amplifier (16), and filtered by the second band-pass filter (17) to remove UO3Obtaining a signal U by low-frequency components and high-frequency noise components in the signalx2Comprises the following steps:
Figure BDA0002269331730000182
k in formula (16)3Is the amplification of said second differential amplifier (16).
Furthermore, when the measured current IpIn the case of a DC signal, U is expressed by equations (6) to (13)x1＝4K1N12SHpωμ1，U x20; the signal Ux1And Ux2After being superposed by the adder (18), the signals are amplified by the regulator (19), and then are generated into driving signals by the driver (20) to drive the compensation current source (21) to generate compensation current Ic(ii) a The compensation current IcGenerating a compensating magnetic field Hc(ii) a The compensation magnetic field HcMagnetic field H generated by current to be measuredpIn the opposite direction, equation (14) can be rewritten as:
Ux1＝K1Uin1＝4K1N12S(Hp-Hc)ωμ1formula (17)
Provided that U in the formula (14)x1If the signal is not zero, the signal passes through the adder (18), the regulator (19) and the driver (20) and then drives the compensation current source (21) to generate the compensation current Ic, and further generates the sum HpCompensating magnetic field H with opposite directionsResult in Ux1Reducing to finally reach dynamic magnetic field balance, so that U is formedx1Approaching 0, i.e. Hp＝Hs(ii) a Said Hp、HsWith said measured current Ic、IpThe relationship of (1) is: hp＝Kp×Ip，Hc＝Kc×Ic，Kp、KcThe linear coefficient can be calibrated according to the original measurement data;
the voltage U at the two ends of the sampling resistor Rs (22)OS＝Ic×RsFurther calculating the measured current IpComprises the following steps:
Figure BDA0002269331730000191
from the equation (18), by measuring the sampling resistance RsVoltage U acrossOSThe measured current I can be invertedpThe size of (2).
Furthermore, when the measured current IpWhen the signal is an alternating current signal, the signal Ux2As shown in equation (16), the signal passes through the adder (18), the regulator (19) and the driver (20) to generate a driving signal, and then drives the compensation current source (21) to generate a compensation current Ic(ii) a The compensation current Ic generates a compensation magnetic field H in the third detection coil (11)c(ii) a The compensation magnetic field and the measured current IpThe generated magnetic field HpIn the opposite direction, equation (16) can be rewritten as:
Figure BDA0002269331730000192
under the action of the regulator (19), the driver (20) and the compensating current source (20), the third magnetic ring (3) finally achieves dynamic magnetic balance, namely Hp＝Hc(ii) a According to the ampere-loop theorem, N can be known3×Ic＝IpIn the formula N3The number of turns of the third compensation coil (12); the sampling resistor Rs(22) Voltage U acrossOSComprises the following steps: u shapeOS＝Ic×RsFurther calculating the measured current IpComprises the following steps:
Figure BDA0002269331730000193
from the equation (20), by measuring the sampling resistance RsVoltage U acrossOSThe measured current I can be invertedpThe size of (2).
The working principle and the measuring method of the present invention have been described above by way of specific embodiments, and those skilled in the art can make appropriate changes according to the needs without departing from the spirit and scope of the present invention, and these changes are all included in the scope of the claims.

Claims (7)

1. A wide-range broadband high-precision magnetic balance type current measuring device is characterized by comprising a first magnetic ring (1), a second magnetic ring (2), a third magnetic ring (3), an excitation current source (4), a first excitation coil (5), a first detection coil (6), a first compensation coil (7), a second excitation coil (8), a second detection coil (9), a second compensation coil (10), a third detection coil (11), a third compensation coil (12), a first differential amplifier (13), a first band-pass filter (14), a phase-sensitive filter (15), a second differential amplifier (16), a second band-pass filter (17), an adder (18), a regulator (19), a driver (20), a compensation current source (21) and a sampling resistor (22),
the first magnetic ring (1), the second magnetic ring (2) and the third magnetic ring (3) are pasted together in parallel, and the current I to be measuredpPasses through the three magnetic rings to generate magnetic fields H with the same size in the three magnetic ringsp；
The first excitation coil (5), the first detection coil (6) and the first compensation coil (7) are wound on the surface of the first magnetic ring (1);
the second excitation coil (8), the second detection coil (9) and the second compensation coil (10) are wound on the surface of the second magnetic ring (2);
the second detection coil (11) and the third compensation coil (12) are wound on the surface of the third magnetic ring (3);
one end of the first exciting coil (5) is connected with the output anode of the exciting current source (4), the other end of the first exciting coil is connected with one end of the second exciting coil (8), and the other end of the second exciting coil (8) is connected with the output cathode of the exciting current source (4);
one end of the first detection coil (6) is connected with the positive input end of the first differential amplifier (13), the other end of the first detection coil is connected with one end of the second detection coil (9), and the other end of the second detection coil (9) is connected with the negative input end of the first differential amplifier (13);
the first compensation coil (7), the second compensation coil (10) and the third compensation coil (12) are respectively connected in series, namely the tail end of the third compensation coil (12) is connected with the head end of the second compensation coil (10), the tail end of the second compensation coil (10) is connected with the head end of the first compensation coil (7), the tail end of the first compensation coil (7) is connected with the positive end of the sampling resistor (22), and the negative end of the sampling resistor (22) is connected with the output negative electrode of the compensation current source (21); the head end of the third compensation coil (12) is connected with the output positive electrode of the compensation current source (21);
the output end of the first differential amplifier (13) is connected with the input end of the first band-pass filter (14); the output end of the first band-pass filter (14) is connected with the input end of the phase sensitive detector (15);
two ends of the third detection coil (11) are respectively connected with the input end of the second differential amplifier (16), and the output end of the second differential amplifier (16) is connected with the second band-pass filter (17);
the output end of the phase-sensitive detector (15) and the output end of the second band-pass filter (17) are respectively connected to the adder (18);
the output end of the adder (18) is connected with the input end of the regulator (19); the output end of the regulator (19) is connected with the input end of the driver (20); the output end of the driver (20) is connected to the input end of the compensation current source (21).
2. The wide-range wide-band high-precision magnetic balance type current measuring device as claimed in claim 1,
the first magnetic ring (1), the second magnetic ring (2) and the third magnetic ring (3) are three identical magnetic rings;
the number of turns of the first excitation coil (5) is completely the same as that of the second excitation coil (8), and the number of turns of the first detection coil (6) is completely the same as that of the second detection coil (9); the number of turns of the first compensation coil (7) is identical to that of the second compensation coil (10);
the excitation current source (4) is used for generating high-frequency periodic alternating excitation current I in the first excitation coil (5) and the second excitation coil (8)eThe current generates a high-frequency periodically alternating excitation magnetic field H in the first magnetic ring (1) and the second magnetic ring (2)eThe amplitude of the excitation magnetic field is far larger than the saturated magnetic field value of the first magnetic ring (1) and the second magnetic ring (2), so that the first magnetic ring (1) and the second magnetic ring (2) are in a saturated state and a non-saturated state and are periodically alternated;
the first magnetic ring (1), the second magnetic ring (2), the first compensating coil (7) and the second compensating coil (10) are used for measuring direct current; the third magnetic ring (3) and the third compensation coil (12) are used for measuring alternating current.
3. The wide-range wide-band high-precision magnetic balance type current measuring device as claimed in claim 1,
after being supplied with power from the outside, the excitation current source (4) generates periodic excitation current I to the first excitation coil (5) and the second excitation coil (6)e＝Imsin ω t, where ω ═ 2 π fe，feTo frequency of the excitation current, ImThe excitation current respectively generates excitation magnetic fields H with equal magnitude and opposite directions in the first magnetic ring (1) and the second magnetic ring (2) for amplitudee＝Hmsinωt，HmIs the amplitude of the excitation magnetic field;
at the measured current IpWhen equal to 0, the magnetic field H generated by the side currentp0; the magnetic induction intensity B in the first magnetic ring (1) and the second magnetic ring (2)1And B2Respectively as follows:
B1＝B2＝μHmsin ω t type (1)
Mu in the formula (1) is the magnetic conductivity of the three magnetic rings;
the magnetic induction intensity B1Induced electromotive force U generated in the first detection coil (6)O1Comprises the following steps:
Figure FDA0002269331720000031
n in the formula (2)12The number of turns of the first detection coil (6) and the second detection coil (9) is set, and S is the sectional area of the three magnetic rings;
the magnetic induction intensity B2Induced electromotive force U generated in the second detection coil 9O2Comprises the following steps:
Figure FDA0002269331720000041
the input signal U of said first differential amplifier (13)in1Comprises the following steps:
Uin1＝UO1+UO2formula (4)
From the expressions (2) to (4), it can be seen that the current signal I is applied to the target sidepIn the case of a value of 0, the value,
the input signal U of the first differential amplifier (13)in1＝0；
At the measured current IpWhen equal to 0, the magnetic field H generated by the side currentpWhen the magnetic induction is 0, the magnetic induction intensity B in the third magnetic ring (3)3When the value is 0, the induced electromotive force U at the two ends of the third detection coil (11) isO3Comprises the following steps:
Figure FDA0002269331720000042
n in formula (5)3The number of turns of the third detection coil (11);
the input signal U of said second differential amplifier (16)in2＝UO3＝0；
The output signal of the first differential amplifier (13) passes through the first band-pass filter (14) and the phase sensitive detector (15), and then the output signal U is outputx1＝0；
The output signal of the second differential amplifier (16) passes through the second band-pass filter (17), and then the output signal U is outputx2＝0；
The output signal Ux1And Ux2After passing through the adder (18), the regulator (19) and the driver (20), the compensation current I output by the compensation current source (21) is still zerocWhen the voltage U is equal to 0, the voltage U is between the two ends of the sampling resistor (22)OS0; i.e. when said measured current IpWhen the value is 0, the output of the current measuring device according to the present invention is also 0.
4. The wide-range wide-band high-precision magnetic balance type current measuring device as claimed in claim 3,
when the measured current IpWhen the magnetic field is not equal to 0 and is a direct current signal, the magnetic fields generated in the first magnetic ring (1), the second magnetic ring (2) and the third magnetic ring (3) are all Hp；
In the excitation magnetic field HeAnd said magnetic field HpUnder the combined action of the magnetic flux and the magnetic induction intensity B in the first magnetic ring (1)1Comprises the following steps:
B1＝μ(Hp+Hmsin ω t) type (6)
The magnetic induction intensity B in the second magnetic ring (2)2Comprises the following steps:
B2＝μ(Hp-Hmsin ω t) type (7)
The magnetic induction intensity B1Induced electromotive force U generated by acting on the first detection coil (6)O1Comprises the following steps:
Figure FDA0002269331720000051
the magnetic induction intensity B2Induced electromotive force U generated in the second detection coil (9)O2Comprises the following steps:
Figure FDA0002269331720000052
the amplitude H of the excitation magnetic fieldmIs far larger than the saturated magnetic field intensity H of the first magnetic ring (1) and the second magnetic ring (2)s(ii) a At the moment, the first magnetic ring (1) and the second magnetic ring (2) are in a non-saturated state and a saturated state to periodically alternate, and the magnetic permeability mu of the first magnetic ring and the second magnetic ring also periodically changes between a linear region and a non-linear region, wherein the magnetic permeability mu can be expressed as:
Figure FDA0002269331720000053
in the formula (10) < mu >dcIs the direct current component of the magnetic permeability, μiIs the 2 i-th harmonic component of the permeability; by substituting formula (10) for formula (8) and formula (9), respectively:
Figure FDA0002269331720000061
Figure FDA0002269331720000062
said first differential amplifier (13) inputting a signal Uin1Comprises the following steps:
Figure FDA0002269331720000063
the input signal Uin1After passing through the first differential amplifier (13), proportional amplification is carried outThen, after passing through the first band-pass filter (14), harmonic components for 4 times or more are filtered out, and only 2 times of components are reserved; the phase sensitive detector (15) extracts the amplitude of the 2-time component and outputs a signal Ux1Comprises the following steps:
Ux1＝K1Uin1＝4K1N12SHpωμ1formula (14)
Formula (14) K1Is the amplification factor of the first differential amplifier (13), mu1Is a secondary component of the permeability;
when the measured current IpWhen the signal is a direct current signal, the magnetic induction intensity B generated in the third magnetic ring (3) is3The induced electromotive force U is generated after passing through the third detection coil (11) and is kept unchangedO30; then the signal U is output after passing through the second differential amplifier (16) and the second band-pass filter (17)x2＝0。
5. The wide-range wide-band high-precision magnetic balance type current measuring device as claimed in claim 3,
when the measured current IpWhen the magnetic field generated by the magnetic field generator is not equal to 0 and is an alternating current signal, the magnetic field generated by the magnetic field generator in the third magnetic ring is HpThe magnetic induction intensity B of the magnetic field generated in the third magnetic ring (3)3＝μHp(ii) a The magnetic induction intensity B3Induced electromotive force U generated at both ends of the third detection coil (11)O3Comprises the following steps:
Figure FDA0002269331720000071
the U isO3The signal is amplified in proportion after passing through the second differential amplifier (16), and filtered by the second band-pass filter (17) to remove UO3Obtaining a signal U by low-frequency components and high-frequency noise components in the signalx2Comprises the following steps:
Figure FDA0002269331720000072
k in formula (16)3Is the amplification of said second differential amplifier (16).
6. The wide-range wide-band high-precision magnetic balance type current measuring device as claimed in claim 4,
when the measured current IpIn the case of a DC signal, U is expressed by equations (6) to (13)x1＝4K1N12SHpωμ1，Ux20; the signal Ux1And Ux2After being superposed by the adder (18), the signals are amplified by the regulator (19), and then are generated into driving signals by the driver (20) to drive the compensation current source (21) to generate compensation current Ic(ii) a The compensation current IcGenerating a compensating magnetic field Hc(ii) a The compensation magnetic field HcMagnetic field H generated by current to be measuredpIn the opposite direction, equation (14) can be rewritten as:
Ux1＝K1Uin1＝4K1N12S(Hp-Hc)ωμ1formula (17)
Provided that U in the formula (14)x1If the signal is not zero, the signal passes through the adder (18), the regulator (19) and the driver (20) and then drives the compensation current source (21) to generate the compensation current IcAnd then produce and HpCompensating magnetic field H with opposite directionsResult in Ux1Reducing, repeatedly adjusting to finally reach dynamic magnetic field balance, and making Ux1Approaching 0, i.e. Hp＝Hs(ii) a Said Hp、HsWith said measured current Ic、IpThe relationship of (1) is: hp＝Kp×Ip，Hc＝Kc×Ic，Kp、KcThe linear coefficient can be calibrated according to the original measurement data;
the voltage U at two ends of the sampling resistor (22)OS＝Ic×Rs，RsThe measured current I is further calculated for the resistance value of the sampling resistor (22)pComprises the following steps:
Figure FDA0002269331720000081
from the equation (18), by measuring the sampling resistance RsVoltage U acrossosThe measured current I can be invertedpThe size of (2).
7. The wide-range wide-band high-precision magnetic balance type current measuring device as claimed in claim 5,
when the measured current IpWhen the signal is an alternating current signal, the signal Ux2As shown in equation (16), the signal passes through the adder (18), the regulator (19) and the driver (20) to generate a driving signal, and then drives the compensation current source (21) to generate a compensation current Ic(ii) a The compensation current IcGenerating a compensation magnetic field H in said third detection coil (11)c(ii) a The compensation magnetic field and the measured current IpThe generated magnetic field HpIn the opposite direction, equation (16) can be rewritten as:
Figure FDA0002269331720000082
under the action of the regulator (19), the driver (20) and the compensating current source (20), the third magnetic ring (3) finally achieves dynamic magnetic balance, namely H after repeated regulationp＝Hc(ii) a According to the ampere-loop theorem, N can be known3×Ic＝IpIn the formula Ns3The number of turns of the third compensation coil (12); the voltage U at two ends of the sampling resistor (22)OSComprises the following steps: u shapeOS＝Ic×RsFurther calculating the measured current IpComprises the following steps:
Figure FDA0002269331720000083
from the equation (20), by measuring the sampling resistance RsVoltage U acrossOSThe measured current I can be invertedpThe size of (2).
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